Communications technologies have developed continuously, especially wireless communications technologies, which has developed from an original first generation mobile communications technology (1G) and a second generation mobile communications technology (2G) to a current third generation mobile communications technology (3G) and a fourth generation mobile communications technology (4G). Because the fourth generation mobile communications technology is still in a debugging and trial stage, coverage of a 4G network is relatively small. When a call is made/answered by using the 4G network, if the 4G network that is used is relatively poor, the voice call on the 4G network may be switched to a 2G or 3G network.
In a process of switching the voice call on the 4G network to the 2G or 3G network, a terminal detects channel quality of a channel that is being used by the terminal and channel quality of a channel in a surrounding neighboring cell, and sends the channel quality of the channel that is being used by the terminal and the channel quality of the channel in the surrounding neighboring cell to a source base station. The source base station selects one channel according to the channel quality of the channels, obtains a wireless identifier of the channel, and sends, to a source MME (mobility management entity), a switching request that carries the wireless identifier. The source MME sends a voice switching request to a corresponding target MSC (mobile switching center), and the target MSC performs voice switching processing after receiving the voice switching request, that is, the target MSC sends a resource allocation request to a corresponding target base station. When the target base station receives the resource allocation request, the target base station starts to prepare a corresponding resource for current switching, and sends a resource preparation complete notification message to the target MSC after the preparation is completed. The target MSC sends, to an IMS (Internet Protocol multimedia subsystem), a switching instruction that carries a terminal identifier. The IMS queries whether information about a voice capability of the terminal matches current-call-state information. If the information about the voice capability of the terminal matches the current-call-state information, the IMS executes a voice switching program, and at the same time, the target MSC instructs to hand over the terminal to the target base station; if the information about the voice capability of the terminal does not match the current-call-state information, the target MSC sends a switching failure notification message to the source base station.
In a process of implementing the present disclosure, the inventor finds that the prior art has at least the following problem:
In a process of switching a voice call on a 4G network to a 2G or 3G network in the foregoing manner, after a source MME sends a voice switching request to a target MSC, the target MSC needs to instruct a target base station to prepare a corresponding resource; a process of initiating voice switching by an IMS is started only after the resource is prepared; when the IMS determines that information about a possessed voice capability does not match current-call-state information, the target base station has reserved, for a relatively long time (which may reach 15 seconds), the resource prepared for current switching, thereby causing a resource waste.